Drone, method for controlling flight, and recording medium storing program

ABSTRACT

A drone is provided that includes a controller, a time measurer that measures a present time, a position measurer that obtains a current position of the drone, and a storage that stores a time period for which the flight of the drone is permitted. The controller performs operations including determining a possible flight area of the drone in accordance with a difference between an end of the time period for which flight of the drone is permitted and the present time, and determining whether the drone is located within the possible flight area on the basis of the current position of the drone.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 15/730,884,filed Oct. 12, 2017, which is a continuation of U.S. National StageInternational Application No. PCT/JP2016/003142, filed Jun. 30, 2016,which claims the benefit of U.S. Provisional Patent Application No.62/193,680, Filed Jul. 17, 2015, as well as priority to JapaneseApplication Nos. 2016-123242 filed Jun. 22, 2016 and 2015-210330 filedOct. 27, 2015. The entire disclosure of each of the above-identifiedapplications, including the specification, drawings, and claims, isincorporated herein by reference in its entirety.

1. Technical Field

The present disclosure relates to a drone flown by remote control, amethod for controlling the flight of the drone flown by remote control,and a recording medium storing a program.

2. Description of the Related Art

Small drones remotely controlled by remote controllers are gaining inpopularity. Such a drone includes a plurality of propellers and freelyflies through the air by controlling rotational speeds of the pluralityof propellers.

Since drones can freely fly through the air, various regulations on theflight of drones are being examined.

International Publication No. 2012/096282, for example, discloses acontroller that receives specification of a movement permission area ofa model device, determines, after receiving a command for moving themodel device, whether the model device will go out of the movementpermission area as a result of the command on the basis of a position ofthe model device, and transmits, if the model device will not go out ofthe movement permission area, the command to the model device through acommunication interface or does not transmit, if the model device willgo out of the movement permission area, the command to the model device.

In addition, regulations that ban the flight of drones at night andpermit the flight of drones only in daytime are being examined.

SUMMARY

The above example of the related art, however, require furtherimprovements.

In one general aspect, the techniques disclosed here feature a droneincluding a controller, a communicator that communicates with acontroller used to remotely control the drone, a time measurer thatmeasures present time, a position measurer that obtains a currentposition of the drone, and a storage that stores a current position ofthe controller obtained through the communicator and

a time period for which the flight of the drone is permitted. Thecontroller performs operations including determining a flight possiblearea of the drone in accordance with a difference between an end of thetime period for which flight of the drone is permitted and the presenttime, and determining whether the drone is located within the flightpossible area on the basis of a distance between the current position ofthe drone and the current position of the controller.

According to the present disclosure, since a flight possible area of adrone is determined in accordance with a difference between an end of atime period for which the flight of the drone is permitted and a presenttime, the drone can return before the end of the time period for whichthe flight of the drone is permitted.

It should be noted that this general or specific aspect may beimplemented as an apparatus, a system, an integrated circuit, a computerprogram, a computer-readable storage medium such as a compact discread-only memory (CD-ROM), or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a flight controlsystem according to a first embodiment of the present disclosure;

FIG. 2 is a general diagram illustrating an example of a drone accordingto the first embodiment of the present disclosure;

FIG. 3 is a block diagram illustrating the configuration of the droneaccording to the first embodiment of the present disclosure;

FIG. 4 is a diagram illustrating an example of a flight possible areatable according to the first embodiment;

FIG. 5 is a block diagram illustrating the configuration of a controlleraccording to the first embodiment of the present disclosure;

FIG. 6 is a flowchart illustrating a process for controlling the flightof the drone according to the first embodiment of the presentdisclosure;

FIG. 7 is a schematic diagram illustrating reduction of a flightpossible area according to the first embodiment;

FIG. 8 is a diagram illustrating the configuration of a flight controlsystem according to a second embodiment of the present disclosure;

FIG. 9 is a block diagram illustrating the configuration of a droneaccording to the second embodiment of the present disclosure;

FIG. 10 is a block diagram illustrating the configuration of acommunication terminal according to the second embodiment of the presentdisclosure;

FIG. 11 is a flowchart illustrating a separation notification processperformed by the drone according to the second embodiment of the presentdisclosure;

FIG. 12 is a first flowchart illustrating a process for controlling theflight of the drone according to the second embodiment of the presentdisclosure;

FIG. 13 is a second flowchart illustrating the process for controllingthe flight of the drone according to the second embodiment of thepresent disclosure;

FIG. 14 is a third flowchart illustrating the process for controllingthe flight of the drone according to the second embodiment of thepresent disclosure;

FIG. 15 is a schematic diagram illustrating separation between first andsecond flight possible areas according to the second embodiment;

FIG. 16 is a schematic diagram illustrating separation between first tothird flight possible areas according to the second embodiment;

FIG. 17 is a schematic diagram illustrating overlap between the first tothird flight possible areas according to the second embodiment;

FIG. 18 is a schematic diagram illustrating a process for moving thedrone into a largest one of the plurality of flight possible areasseparated from one another; and

FIG. 19 is a block diagram illustrating the configuration of a droneaccording to a modification of the second embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Underlying Knowledge Forming Basis of Present Disclosure

When the flight of a drone is permitted until sunset, for example, anoperator might instruct the drone to return thereto before sunset butthe drone might not be able to return before sunset depending on aposition thereof at the time of the instruction.

In view of the above examination, the present inventor has conceivedaspects of the present disclosure.

A drone according to an aspect of the present disclosure is a droneincluding a controller, a communicator that communicates with a controldevice used to remotely control the drone, a time measurer that measurespresent time, a position measurer that obtains a current position of thedrone, and a storage that stores a current position of the controldevice obtained through the communicator and a time period for which theflight of the drone is permitted. The controller performs operationsincludes determining a flight possible area of the drone in accordancewith a difference between an end of the time period for which flight ofthe drone is permitted and the present time, and determining whether thedrone is located within the flight possible area on the basis of adistance between the current position of the drone and the currentposition of the control device.

With this configuration, the flight possible area of the drone isdetermined in accordance with the difference between the end of the timeperiod for which the flight of the drone is permitted and the presenttime, and whether the drone is located within the flight possible areais determined on the basis of the distance between the current positionof the drone and the current position of the control device.

Since the flight possible area of the drone is determined in accordancewith the difference between the end of the time period for which theflight of the drone is permitted and the present time, the drone canreturn before the end of the time period for which the flight of thedrone is permitted.

In addition, in the drone, the operations may further includesequentially reducing the flight possible area as time elapses.

With this configuration, the flight possible area is sequentiallyreduced as time elapses, and the drone can certainly return before theend of the time period for which the flight of the drone is permitted.

In addition, in the drone, the operations may further includeautomatically moving, if it is determined that the drone is locatedoutside the flight possible area, the drone toward the control device.

With this configuration, if it is determined that the drone is locatedoutside the flight possible area, the drone is automatically movedtoward the control device, and the drone can be automatically moved intothe flight possible area.

In addition, in the drone, the operations may further include rejecting,if it is determined that the drone is located outside the flightpossible area, an operation other than the operation for automaticallymoving the drone toward the control device.

With this configuration, if it is determined that the drone is locatedoutside the flight possible area, an operation other than the operationfor automatically moving the drone toward the control device is notreceived, and the drone can be guided into the flight possible area.

In addition, in the drone, the operations may further include notifying,before the flight possible area is determined, the control device thatthe flight possible area is to be determined.

With this configuration, since the control device is notified, beforethe flight possible area is determined, that the flight possible area isto be determined, the operator can be notified in advance that theflight possible area is to be determined, and the operator can beprompted to move the drone into the flight possible area before theflight possible area is determined.

In addition, in the drone, the flight possible area may include a firstflight possible based on a position of the control device and a secondflight possible area based on a position of a communication terminalcarried by an observer who monitors the drone. The operations mayfurther include determining the first and second flight possible areasin accordance with the difference between the end of the time period forwhich the flight of the drone is permitted and the present time.

With this configuration, the flight possible area includes the firstflight possible area based on the position of the control device and thesecond flight possible area based on the position of the communicationterminal carried by the observer who monitors the drone. The first andsecond flight possible areas are determined in accordance with thedifference between the end of the time period for which the flight ofthe drone is permitted and the present time.

Since, if there is an observer who monitors the drone along with theoperator, the second flight possible area based on the position of thecommunication terminal operated by the observer is determined along withthe first flight possible area based on the position of the controldevice, the drone can return to the control device or the communicationterminal before the end of the time period for which the flight of thedrone is permitted.

In addition, in the drone, the operations may further includeestimating, before the first and second flight possible areas aredetermined, whether the drone is located outside the first and secondflight possible areas, and transmitting, if it is estimated that thedrone is located outside the first and second flight possible areas,guidance information for guiding the drone into the first or secondflight possible area to the control device or the communicationterminal.

With this configuration, it is estimated, before the first and secondflight possible areas are determined, whether the drone is locatedoutside the first and second flight possible areas. If it is estimatedthat the drone is located outside the first and second flight possibleareas, the guidance information for guiding the drone into the first orsecond flight possible area is transmitted to the control device or thecommunication terminal.

The drone, therefore, can be moved into the first or second flightpossible area before the first and second flight possible areas aredetermined.

In addition, in the drone, the operations may further include changing,in accordance with a distance between the control device and the drone,a time at which the guidance information is transmitted.

With this configuration, since the time at which the guidanceinformation is transmitted is changed in accordance with the distancebetween the control device and the drone, the drone can certainly returnto the control device by, for example, transmitting the guidanceinformation earlier as the distance between the control device and thedrone becomes larger.

In addition, in the drone, before the first and second flight possibleareas are determined, movement area information indicating whether thedrone is to be moved into the first or second flight possible area maybe stored in the storage. The operations may further includeautomatically moving, if the drone is not located within the first orsecond flight possible area indicated by the movement area informationwhen the first and second flight possible areas are actually determined,the drone toward the first or second flight possible area indicated bythe movement area information.

With this configuration, before the first and second flight possibleareas are determined, the movement area information indicating whetherthe drone is to be moved into the first or second flight possible areais stored in the storage. If the drone is not located within the firstor second flight possible area indicated by the movement areainformation when the first and second flight possible areas are actuallydetermined, the drone is automatically moved toward the first or secondflight possible area indicated by the movement area information.

Whether the drone is to be moved into the first or second flightpossible area, therefore, can be determined before the first and secondflight possible areas are determined, and the drone can automaticallyreturn to a predetermined position.

In addition, in the drone, the operations may further include reducingonly the first or second flight possible area indicated by the movementarea information as time elapses.

With this configuration, only the first or second flight possible areaindicated by the movement area information is reduced as time elapses,the other flight possible area that is not indicated by the movementarea information is not unnecessarily reduced.

In addition, in the drone, the operations may further includeautomatically moving, if it is determined that the drone is locatedoutside the first and second flight possible areas when the first andsecond flight possible areas are determined, the drone toward thecontrol device or the communication terminal, whichever is closer to thedrone.

With this configuration, if it is determined that the drone is locatedoutside the first and second flight possible areas when the first andsecond flight possible areas are determined, the drone is automaticallymoved toward the control device or the communication terminal, whicheveris closer to the drone.

If it is determined that the drone is located outside the first andsecond flight possible areas when the first and second flight possibleareas are determined, the drone can be certainly moved toward thecontrol device or the communication terminal.

In addition, in the drone, movement area information indicating whetherthe drone is to be moved into the first or second flight possible areamay be stored in the storage before the first and second flight possibleareas are determined. The operations may further include controlling, ifit is determined that the drone is located in an area different from thearea indicated by the movement area information when the first andsecond flight possible area are actually determined, the drone such thatthe drone flies within the area within which the drone is currentlylocated.

With this configuration, the movement area information indicatingwhether the drone is to be moved into the first or second flightpossible area is stored in the storage before the first and secondflight possible areas are determined. If it is determined that the droneis located in an area different from the area indicated by the movementarea information when the first and second flight possible area areactually determined, the drone is controlled such that the drone flieswithin the area within which the drone is currently located.

Since the drone is controlled such that the drone flies within the areawithin which the drone is currently located even if whether the drone isto be moved into the first or second flight possible area is determinedbefore the first and second flight possible areas are determined, thedrone can be certainly moved toward the control device or thecommunication terminal before the end of the time period.

A method for controlling flight according to another aspect of thepresent disclosure is a method for controlling flight of a drone flownby remote control. The method includes communicating various pieces ofinformation with a control device used to remotely control the drone,obtaining present time, a time period for which the flight of the droneis permitted, and a current position of the drone, determining a flightpossible area of the drone in accordance with a difference between anend of the time period for which the flight of the drone is permittedand the present time, and determining whether the drone is locatedwithin the flight possible area on the basis of a distance between thecurrent position of the drone and a current position of the controldevice.

With this configuration, the present time is obtained, the flightpossible area of the drone is determined in accordance with thedifference between the end of the time period for which the flight ofthe drone is permitted and the present time, and whether the drone islocated within the flight possible area is determined on the basis ofthe distance between the current position of the drone and the currentposition of the control device.

Since the flight possible area of the drone is determined in accordancewith the difference between the end of the time period for which theflight of the drone is permitted and the present time, the drone canreturn before the end of the time period for which the flight of thedrone is permitted.

A computer-readable non-transitory recording medium according to anotheraspect of the present disclosure is a computer-readable non-transitoryrecording medium storing a program for controlling flight of a droneflown by remote control. The program causes, when executed by acomputer, the computer to perform operations including determining aflight possible area of the drone in accordance with a differencebetween an end of a time period for which the flight of the drone ispermitted and a present time, and determining whether the drone islocated within the flight possible area on the basis of a distancebetween a current position of the drone and a current position of acontrol device used to remotely control the drone.

With this configuration, the present time is obtained, the flightpossible area of the drone is determined in accordance with thedifference between the end of the time period for which the flight ofthe drone is permitted and the present time, and whether the drone islocated within the flight possible area is determined on the basis ofthe distance between the current position of the drone and the currentposition of the control device.

Since the flight possible area of the drone is determined in accordancewith the difference between the end of the time period for which theflight of the drone is permitted and the present time, the drone canreturn before the end of the time period for which the flight of thedrone is permitted.

In addition, in the computer-readable non-transitory recording medium,the operations may further include moving, if it is determined that thedrone is located outside the flight possible area, the drone toward thecontrol device.

With this configuration, if it is determined that the drone is locatedoutside the flight possible area, the drone is moved toward the controldevice, and the drone can be automatically moved into the flightpossible area.

Embodiments of the present disclosure will be described hereinafter withreference to the accompanying drawings. The following embodiments arespecific examples of the present disclosure and do not limit thetechnical scope of the present disclosure.

First Embodiment

FIG. 1 is a diagram illustrating the configuration of a flight controlsystem according to a first embodiment of the present disclosure. Theflight control system illustrated in FIG. 1 includes a drone 10 and acontroller 20.

An operator 1 uses the controller 20 to operate the drone 10 remotely.The controller 20 wirelessly transmits, for example, an operationcommand for operating the drone 10.

The drone 10 is flown by remote control. The drone 10 receives anoperation command from the controller 20 and flies on the basis of thereceived operation command.

FIG. 2 is a general diagram illustrating an example of the drone 10according to the first embodiment of the present disclosure. FIG. 3 is ablock diagram illustrating the configuration of the drone 10 accordingto the first embodiment of the present disclosure.

As illustrated in FIG. 2 , the drone 10 at least includes varioussensors 1001 and propulsion units 1002. The drone 10 stores a timemeasuring unit 101, a position measuring unit 102, a driving unit 103, afirst communication unit 104, a second communication unit 105, a battery106, a control unit 107, and a storage unit 108.

The various sensors 1001 are an image sensor and human detection sensor,for example, and any sensors may be mounted in accordance with the usageof the drone 10.

The propulsion units 1002 each include a propeller for producing lift,thrust, and torque for flying the drone 10 and a motor for rotating thepropeller. In the example illustrated in FIG. 2 , the drone 10 includesfour propulsion units 1002, but the number of propulsion units 1002 maybe five or more.

The time measuring unit 101 measures time and obtains present time. Theposition measuring unit 102 is a global positioning system (GPS), forexample, and obtains a current position of the drone 10. The currentposition of the drone 10 is represented by latitude, longitude, andaltitude.

The driving unit 103 drives the propulsion units 1002 for flying thedrone 10. The driving unit 103 rotates the propellers for flying thedrone 10.

The first communication unit 104 receives an operation command from thecontroller 20, for example, through specified low-power radiocommunication. The second communication unit 105 transmits variouspieces of information to the controller 20 and receives various piecesof information from the controller 20 through a communication standardsuch as long-term evolution (LTE).

The battery 106 is a power supply of the drone 10 and supplies power tothe components of the drone 10. The drone 10 need not include a battery,and a battery provided outside the drone 10 may supply power to thedrone 10, instead.

The control unit 107 is a central processing unit (CPU) and controls theoperation of the drone 10. The control unit 107 includes a flightcontrol section 111, a flight possible area changing section 112, aforcible movement control section 113, and a notification section 114.

The storage unit 108 is a semiconductor memory, for example, and storesvarious pieces of information. The storage unit 108 stores a flightbasic program 121, a flight possible area table 122, controllerpositional information 123, a forcible movement program 124, flightpossible area information 125, sunset information 126.

The flight basic program 121 is used to control the flight of the drone10. The flight control section 111 executes the flight basic program 121to control the flight of the drone 10.

The flight possible area table 122 is a table in which certain timeperiods before sunset and flight possible areas (flight possibledistances) are associated with each other.

FIG. 4 is a diagram illustrating an example of the flight possible areatable 122 according to the first embodiment. As illustrated in FIG. 4 ,a time period from 30 minutes to 20 minutes before sunset is associatedwith a flight possible area of 50 m. A flight possible area refers to adistance from the controller 20 within which the drone 10 may move. Atime period from 20 minutes to 15 minutes before sunset is associatedwith a flight possible area of 40 m. A time period from 15 minutes to 10minutes before sunset is associated with a flight possible area of 30 m.A time period from 10 minutes to 5 minutes before sunset is associatedwith a flight possible area of 20 m. A time period from 5 minutes beforesunset to sunset is associated with a flight possible area of 10 m.

The above flight possible area table 122 is an example, and time periodsand flight possible areas are not limited to those described above.

The controller positional information 123 indicates a current positionof the controller 20. The second communication unit 105 regularlyreceives the controller positional information 123 transmitted from thecontroller 20 and stores the received controller positional information123 in the storage unit 108.

The sunset information 126 indicates a time of sunset of the day. Whenthe date changes, for example, the second communication unit 105 obtainssunset information indicating a time of sunset of the day from anexternal server and stores the obtained sunset information in thestorage unit 108. Alternatively, the second communication unit 105 mayobtain sunset information input by the operator 1 and store the obtainedsunset information in the storage unit 108. Alternatively, the storageunit 108 may store, in advance, sunset information in which dates andtimes of sunset are associated with each other.

As with the sunset information 126, the flight basic program 121, theflight possible area table 122, and the forcible movement program 124may be obtained from an external server.

The flight possible area changing section 112 determines a flightpossible area of the drone 10 in accordance with a difference between anend of a time period for which the flight of the drone 10 is permittedand the present time. In the present embodiment, the end of the timeperiod is the time of sunset at the position of the drone 10. The flightpossible area changing section 112 determines the flight possible areaof the drone 10 in accordance with a difference between the time ofsunset and the present time. The flight possible area changing section112 reads the sunset information 126 from the storage unit 108, obtainsthe present time from the time measuring unit 101, and calculates thedifference between the time of sunset and the present time. The flightpossible area changing section 112 then refers to the flight possiblearea table 122 and extracts a flight possible area associated with thedifference between the time of sunset and the present time.

In addition, the flight possible area changing section 112 sequentiallyreduces the flight possible area as time elapses. In the presentembodiment, the flight possible area changing section 112 reduces theflight possible area by determining the flight possible area as 50 m 30minutes before sunset and as 40 m 20 minutes before sunset. The flightpossible area changing section 112 thus sequentially reduces the flightpossible area as sunset approaches.

The flight possible area information 125 indicates the current flightpossible area of the drone 10 determined by the flight possible areachanging section 112.

The flight control section 111 controls the drone 10 such that the drone10 flies within the flight possible area. If the flight control section111 receives an operation command for flying out of the flight possiblearea, for example, the flight control section 111 rejects the operationcommand and controls the drone 10 such that the drone 10 stays withinthe flight possible area. For example, the flight control section 111calculates a distance between the drone 10 and the controller 20 on thebasis of the current positions of the drone 10 and the controller 20.The flight control section 111 then determines whether the calculateddistance is equal to or smaller than the flight possible distance inorder to determine whether the drone 10 is located within the flightpossible area.

The forcible movement program 124 is used to fly the drone 10 forcibly.The forcible movement control section 113 executes the forcible movementprogram 124 to fly the drone 10 forcibly in a certain direction. If theflight control section 111 determines that the drone 10 is locatedoutside the flight possible area after the flight possible area changingsection 112 determines the flight possible area, the forcible movementcontrol section 113 automatically moves the drone 10 toward thecontroller 20. If the drone 10 is located outside the flight possiblearea, the forcible movement control section 113 does not accept anyoperations other than an operation for moving the drone 10 toward thecontroller 20.

Although the control unit 107 separately includes the flight controlsection 111 and the forcible movement control section 113 in the presentembodiment, the control unit 107 may include only the flight controlsection 111, and the flight control section 111 may have the function ofthe forcible movement control section 113.

If the drone 10 is forcibly caused to fly toward the controller 20, thenotification section 114 notifies the controller 20 that the drone 10 isto be forcibly caused to fly toward the controller 20.

In addition, the notification section 114 may determine whether theflight possible area is to be changed and, if so, notify the controller20 that the flight possible area is to be changed. Before the flightpossible area changing section 112 determines the flight possible area,the notification section 114 notifies the controller 20 that the flightpossible area is to be determined.

It is assumed, for example, that the flight possible area is changedevery 10 minutes from 30 minutes before sunset. In this case, the flightpossible area is changed 30 minutes, 20 minutes, and 10 minutes beforesunset. If the operator 1 understands a new flight possible area inadvance, the operator 1 can guide the drone 10 into the new flightpossible area before the flight possible area is changed. The drone 10,therefore, determines the flight possible area and notifies thecontroller 20 of the flight possible area, for example, 5 minutes beforethe flight possible area is actually changed. In this example, the drone10 determines the flight possible areas and notifies the controller 20of the flight possible areas 35 minutes, 25 minutes, and 15 minutesbefore sunset.

FIG. 5 is a block diagram illustrating the configuration of thecontroller 20 according to the first embodiment of the presentdisclosure. The operator 1 holds the controller 20 with both his/herhands. The controller 20 includes a control unit 201, a positionmeasuring unit 202, a battery 203, a display unit 204, an operationcommand input unit 205, a first wireless communication unit 206, and asecond wireless communication unit 207.

The control unit 201 is a CPU, for example, and controls the operationof the controller 20. The position measuring unit 202 is a GPS, forexample, and obtains the current position of the controller 20. Thecurrent position of the controller 20 is represented by latitude,longitude, and altitude. The battery 203 is a power supply of thecontroller 20 and supplies power to the components of the controller 20.

The operation command input unit 205 includes a left stick provided on aleft-hand side of the operator 1 and a right stick provided on aright-hand side of the operator 1. When the operator 1 moves the leftand right sticks, the operation command input unit 205 outputs angularinformation regarding inclination angles to the first wirelesscommunication unit 206. The movement of the drone 10 is controlled inaccordance with the inclination angles. An operation command includes,for example, angular information indicating the inclination angles ofthe left and right sticks.

The first wireless communication unit 206 transmits an operation commandto the drone 10 through, for example, specified low-power radiocommunication. The second wireless communication unit 207 transmitsvarious pieces of information to the drone 10 and receives variouspieces of information from the drone 10 through a communication standardsuch as LTE. The second wireless communication unit 207 transmits, tothe drone 10, the controller positional information 123 indicating thecurrent position of the controller 20 measured by the position measuringunit 202. The second wireless communication unit 207 receives, from thedrone 10, information indicating that the flight possible area is to bechanged or information indicating that the drone 10 is forcibly causedto fly toward the controller 20.

Although the second wireless communication unit 207 regularly transmitsthe current position of the controller 20 measured by the positionmeasuring unit 202 to the drone 10 in the present embodiment, thepresent disclosure is not particularly limited to this. The secondwireless communication unit 207 may receive, from the drone 10, apositional information request for requesting the current position ofthe controller 20 and then transmit the current position of thecontroller 20 measured by the position measuring unit 202 to the drone10, instead.

The display unit 204 displays information, which has been received bythe second wireless communication unit 207, indicating that the flightpossible area is to be changed. The display unit 204 also displaysinformation, which has been received by the second wirelesscommunication unit 207, indicating that the drone 10 is forcibly causedto fly toward the controller 20.

The controller 20 may be, for example, a smartphone, a tablet computer,or a personal computer. The controller 20 may display an operationscreen on a touch panel and receive an operation performed by theoperator 1.

Next, a process for controlling the flight of the drone 10 according tothe first embodiment will be described.

FIG. 6 is a flowchart illustrating the process for controlling theflight of the drone 10 according to the first embodiment of the presentdisclosure.

First, in step S1, the time measuring unit 101 obtains the present time.

Next, in step S2, the flight possible area changing section 112 refersto the flight possible area table 122 and determines whether the flightpossible area is to be changed now. The flight possible area is changedcertain periods of time before sunset. The flight possible area refersto a distance within which the drone 10 can return to the controller 20(operator 1) before sunset. If the flight possible area changing section112 determines that the flight possible area is not to be changed now(NO in step S2), the process returns to step S1.

If the flight possible area changing section 112 determines that theflight possible area is to be changed now (YES in step S2), on the otherhand, the flight possible area changing section 112, in step S3,determines the flight possible area of the drone 10 in accordance withthe difference between the time of sunset and the present time. If thedifference between the time of sunset and the present time is 30minutes, for example, the flight possible area changing section 112refers to the flight possible area table 122 and determines a hemispherewhose center is the current position of the controller 20 and whoseradius is 50 m as the flight possible area. The flight possible areachanging section 112 then stores the determined flight possible area inthe storage unit 108 as the flight possible area information 125.

If the current positions of the drone 10 and the controller 20 includelatitude information, longitude information, and altitude information,the flight possible area has a hemispherical shape whose center is thecurrent position of the controller 20 and whose radius is the flightpossible distance. If the current positions of the drone 10 and thecontroller 20 include latitude information and longitude information butdo not include altitude information, the flight possible area has acircular shape whose center is the current position of the controller 20and whose radius is the flight possible distance.

Next, in step S4, the position measuring unit 102 obtains the currentposition of the drone 10.

Next, in step S5, the flight possible area changing section 112 readsthe controller positional information 123 from the storage unit 108 toobtain the current position of the controller 20. Although thecontroller positional information 123 stored in the storage unit 108does not necessarily indicate the current position of the controller 20,the accuracy of identification of the current position of the controller20 can be increased by obtaining the controller positional information123 from the controller 20 more frequently. Alternatively, in step S5,the second communication unit 105 may request the current position fromthe controller 20 and receive the current position from the controller20.

Next, in step S6, the flight possible area changing section 112calculates the distance between the drone 10 and the controller 20 onthe basis of the current positions of the drone 10 and the controller20.

Next, in step S7, the flight possible area changing section 112determines, on the basis of the distance between the drone 10 and thecontroller 20 and the flight possible area, whether the drone 10 islocated within the flight possible area. That is, the flight possiblearea changing section 112 compares the distance between the drone 10 andthe controller 20 with the flight possible distance and, if the distancebetween the drone 10 and the controller 20 is equal to or smaller thanthe flight possible distance, determines that the drone 10 is locatedwithin the flight possible area or, if the distance between the drone 10and the controller 20 is larger than the flight possible distance,determines that the drone 10 is not located within the flight possiblearea.

If the flight possible area changing section 112 determines that thedrone 10 is located within the flight possible area (YES in step S7),the flight control section 111, in step S8, accepts an operation commandfrom the controller 20 and flies the drone 10 in accordance with theoperation command. At this time, the flight control section 111 movesthe drone 10 in accordance with an operation performed by the operator1. The flight control section 111 generates driving signals for drivingthe propellers on the basis of the operation command received by thefirst communication unit 104 and outputs the generated driving signalsto the driving unit 103. The drone 10 can move forward, rearward,leftward, rightward, upward, and downward by controlling rotationalspeeds of the propellers. The flight control section 111 may detectchanges in a flight attitude on the basis of outputs from a three-axisgyro sensor (not illustrated) and a three-axis acceleration sensor (notillustrated) and automatically stabilize the flight attitude of thedrone 10.

If the flight possible area changing section 112 determines that thedrone 10 is not located within the flight possible area (NO in step S7),on the other hand, the forcible movement control section 113, in stepS9, forcibly moves the drone 10 toward the controller 20 so that thedrone 10 enters the flight possible area. At this time, the forciblemovement control section 113 does not accept an operation command fromthe controller 20 until the drone 10 enters the flight possible area.

Next, in step S10, the notification section 114 notifies the controller20 that the drone 10 is forcibly moved toward the controller 20. Theprocess returns to step S7, and the forcible movement control section113 automatically flies the drone 10 toward the controller 20 until thedrone 10 enters the flight possible area.

FIG. 7 is a schematic diagram illustrating the reduction of the flightpossible area according to the first embodiment. In FIG. 7 , the drone10 and the controller 20 are viewed from above. In FIG. 7 , the flightpossible area changing section 112 determines, at a first time, which isa certain period of time before sunset, a flight possible area 2 whosecenter is the controller 20 and whose radius is a flight possibledistance FD1. The flight possible area changing section 112 thendetermines, at a second time, which is closer to the time of sunset thanthe first time is, a flight possible area 21 whose center is thecontroller 20 and whose radius is a flight possible distance FD2, whichis smaller than the flight possible distance FD1.

The flight possible area changing section 112 thus reduces the flightpossible area as sunset approaches. As a result, the drone 10 can returnto the controller 20 before sunset, and it becomes possible to preventthe drone 10 from flying after sunset.

Although the drone 10 can move without any limitation until the flightpossible area is determined for the first time in step S3 illustrated inFIG. 6 in the first embodiment, an initial flight possible area may bedetermined in advance before the flight possible area is determined forthe first time in step S3 illustrated in FIG. 6 . The initial flightpossible area is, for example, a visible area predetermined inaccordance with regulations, a visible area determined by the operator1, or an area in which radio communication can be performed.

Although the end of the time period for which the flight of the drone 10is permitted is the time of sunset in the first embodiment, the presentdisclosure is not particularly limited to this. For example, apredetermined time, namely 5 p.m. or 6 p.m., for example, may be the endof the time period, instead. Alternatively, the end of the time periodmay be a time of sunset at the position of the controller 20.

In addition, although the flight possible area has a circular shape, thepresent disclosure is not particularly limited to this. For example, theflight possible area may have an elliptical shape, instead. That is, themoving speed of the drone 10 might change in accordance with winddirection and wind speed. The flight possible area changing section 112,therefore, may change the shape of the flight possible area inaccordance with wind direction and wind speed.

In addition, in the first embodiment, the controller 20 may include thetime measuring unit 101, the flight possible area changing section 112,the forcible movement control section 113, the flight possible areatable 122, the forcible movement program 124, the flight possible areainformation 125, and the sunset information 126. In this case, theforcible movement control section 113 has a function of generating andtransmitting a command for forcibly moving the drone 10. The forciblemovement program 124 is used to generate and transmit a command forforcibly moving the drone 10. The flight possible area table 122, theforcible movement program 124, the flight possible area information 125,and the sunset information 126 are stored in a storage unit of thecontroller 20. The storage unit also stores positional informationregarding the drone 10. As a result, the controller 20 can perform theprocesses performed by the drone 10 in the above description.

In addition, if the drone 10 is located outside the flight possible areawhen the flight possible area changing section 112 has determined theflight possible area, the forcible movement control section 113 maytransmit, to the drone 10, a control signal for automatically moving thedrone 10 toward the controller 20. Furthermore, if the drone 10 islocated outside the flight possible area, the forcible movement controlsection 113 need not transmit a control signal for instructing the drone10 to perform an operation other than moving toward the controller 20.

In addition, in the first embodiment, the flight control system mayinclude the drone 10, the controller 20, and a server. The server isconnected to the controller 20 through a network. The server may includethe time measuring unit 101, the flight possible area changing section112, the forcible movement control section 113, the flight possible areatable 122, the forcible movement program 124, the flight possible areainformation 125, and the sunset information 126. In this case, theforcible movement control section 113 has a function of generating andtransmitting a command for forcibly moving the drone 10. The forciblemovement program 124 is used to generate and transmit a command forforcibly moving the drone 10. The flight possible area table 122, theforcible movement program 124, the flight possible area information 125,and the sunset information 126 are stored in a storage unit of theserver. The storage unit also stores positional information regardingthe drone 10. As a result, the server can perform the processesperformed by the drone 10 in the above description. Informationtransmitted from the server may be received by the drone 10 through thecontroller 20, and information transmitted from the drone 10 may bereceived by the server through the controller 20. Alternatively,information transmitted from the server may be directly received by thedrone 10, and information transmitted from the drone 10 may be directlyreceived by the server.

Second Embodiment

Next, a flight control system according to a second embodiment will bedescribed.

FIG. 8 is a diagram illustrating the configuration of the flight controlsystem according to the second embodiment of the present disclosure. Theflight control system illustrated in FIG. 8 includes a drone 10, thecontroller 20, and a communication terminal 30.

When the drone 10 flies outside a visible area of the operator 1, avisual observer (VO) 3 monitors the drone 10 on behalf of the operator1. The VO 3 is located far from the operator 1 and notifies the operator1 of the position of the drone 10. The VO 3 may call the operator 1 inorder to tell the operator 1 the position of the drone 10. The VO 3carries the communication terminal 30 capable of communicating with thecontroller 20 and tells the operator 1 the position of the drone 10through the communication terminal 30 and the controller 20.

If there is a VO 3 as well as the operator 1, a first flight possiblearea 2 around the operator 1 and a second flight possible area 4 aroundthe VO 3 can be determined. When the first and second flight possibleareas 2 and 4 determined by the operator 1 and the VO 3, respectively,have been reduced as sunset approaches, the first and second flightpossible areas 2 and 4 might be separated from each other and the drone10 might not be located within either the first flight possible area 2or the second flight possible area 4. In the second embodiment,therefore, when the first and second flight possible areas 2 and 4 willbe separated from each other, the controller 20 is notified that thefirst and second flight possible areas 2 and 4 will be separated fromeach other and the drone 10 needs to be moved into the first flightpossible area 2 around the controller 20.

FIG. 9 is a block diagram illustrating the configuration of the drone 10according to the second embodiment of the present disclosure. The drone10 illustrated in FIG. 9 includes the time measuring unit 101, theposition measuring unit 102, the driving unit 103, the firstcommunication unit 104, the second communication unit 105, the battery106, the control unit 107, and the storage unit 108. In the secondembodiment, description of the same components as in the firstembodiment is omitted.

The second communication unit 105 transmits various pieces ofinformation to the controller 20 and receives various pieces ofinformation from the controller 20 through a communication standard suchas LTE. The second communication unit 105 also transmits various piecesof information to the communication terminal 30 and receives variouspieces of information from the communication terminal 30 through acommunication standard such as LTE.

The control unit 107 includes the flight control section 111, the flightpossible area changing section 112, the forcible movement controlsection 113, and the notification section 114.

The storage unit 108 stores the flight basic program 121, the flightpossible area table 122, the controller positional information 123, theforcible movement program 124, the flight possible area information 125,the sunset information 126, and a VO positional information 127.

The VO positional information 127 is information indicating a currentposition of the communication terminal 30. The second communication unit105 regularly receives the VO positional information 127 transmittedfrom the communication terminal 30 and stores the received VO positionalinformation 127 in the storage unit 108. Alternatively, thecommunication terminal 30 may transmit the VO positional information 127to a server, and the drone 10 may receive the VO positional information127 through the controller 20.

The flight possible area changing section 112 determines the firstflight possible area 2 based on the position of the controller 20 andthe second flight possible area 4 based on the position of thecommunication terminal 30 operated by the VO 3 who monitors the drone 10in accordance with a difference between the end of the time period forwhich the flight of drone 10 is permitted and the present time.

The notification section 114 estimates, before the flight possible areachanging section 112 determines the first and second flight possibleareas 2 and 4, whether the drone 10 is located outside the first andsecond flight possible areas 2 and 4. If estimating that the drone 10 islocated outside the first and second flight possible areas 2 and 4, thenotification section 114 transmits, to the controller 20, guidanceinformation for guiding the drone 10 into the first flight possible area2. Alternatively, if estimating that the drone 10 is located outside thefirst and second flight possible areas 2 and 4, the notification section114 may transmit, to the communication terminal 30, guidance informationfor guiding the drone 10 into the first flight possible area 2. Thenotification section 114 may change a timing at which the notificationsection 114 transmits the guidance information in accordance with thedistance between the controller 20 and the drone 10.

If the drone 10 is located outside the first and second flight possibleareas 2 and 4 when the first and second flight possible areas 2 and 4are determined, the forcible movement control section 113 automaticallymoves the drone 10 toward the controller 20. When the drone 10 isforcibly caused to fly toward the controller 20, the notificationsection 114 notifies the controller 20 that the drone 10 is forciblycaused to fly toward the controller 20. Alternatively, when drone 10 isforcibly caused to fly toward the controller 20, the notificationsection 114 may notify the communication terminal 30 that the drone 10is forcibly caused to fly toward the controller 20.

The configuration of the controller 20 according to the secondembodiment is the same as that of the controller 20 according to thefirst embodiment, and description thereof is omitted.

FIG. 10 is a block diagram illustrating the configuration of thecommunication terminal 30 according to the second embodiment of thepresent disclosure.

The communication terminal 30 is, for example, a smartphone, a tabletcomputer, or a personal computer. The communication terminal 30 includesa battery 301, a control unit 302, a position measuring unit 303, amicrophone 304, a speaker 305, a display unit 306, an input unit 307,and a wireless communication unit 308.

The battery 301 is a power supply of the communication terminal 30 andsupplies power to the components of the communication terminal 30. Thecontrol unit 302 is a CPU, for example, and controls the operation ofthe communication terminal 30.

The position measuring unit 303 is a GPS, for example, and obtains thecurrent position of the communication terminal 30. The current positionof the communication terminal 30 is represented by latitude, longitude,and altitude.

The microphone 304 obtains a speech sound uttered by the VO 3 andconverts the obtained speech sound into a speech signal. The speaker 305converts a speech signal transmitted from the controller 20 into aspeech sound and outputs the obtained speech sound to the outside.

The display unit 306 displays various pieces of information relating totelephone calls. The input unit 307 receives various pieces ofinformation relating to telephone calls.

The wireless communication unit 308 transmits various pieces ofinformation to the drone 10 and receives various pieces of informationfrom the drone 10 through a communication standard such as LTE. Thewireless communication unit 308 transmits various pieces of informationto the controller 20 and receives various pieces of information from thecontroller 20. The wireless communication unit 308 transmits, to thedrone 10, the VO positional information 127 indicating the currentposition of the communication terminal 30 measured by the positionmeasuring unit 303. The wireless communication unit 308 also transmits aspeech signal to the controller 20 and receives a speech signal from thecontroller 20.

It is sufficient that the communication terminal 30 at least includesthe position measuring unit 303 and the wireless communication unit 308.The controller 20 preferably includes a microphone and a speaker used tocommunicate with the communication terminal 30.

Next, a separation notification process performed by the drone 10according to the second embodiment will be described. The separationnotification process is a process for notifying the controller 20 thatthe first and second flight possible areas 2 and 4 will be separatedfrom each other.

FIG. 11 is a flowchart illustrating the separation notification processperformed by the drone 10 according to the second embodiment of thepresent disclosure.

First, in step S21, the notification section 114 reads the controllerpositional information 123 from the storage unit 108 to obtain thecurrent position of the controller 20. Although the controllerpositional information 123 stored in the storage unit 108 does notnecessarily indicate the current position of the controller 20, theaccuracy of identification of the current position of the controller 20can be increased by obtaining the controller positional information 123from the controller 20 more frequently. In addition, in step S21, thesecond communication unit 105 may request the current position of thecontroller 20 from the controller 20 and receive the current position ofthe controller 20 from the controller 20.

Next, in step S22, the notification section 114 reads the VO positionalinformation 127 from the storage unit 108 to obtain the current positionof the communication terminal 30. Although the VO positional information127 stored in the storage unit 108 does not necessarily indicate thecurrent position of the communication terminal 30, the accuracy ofidentification of the current position of the communication terminal 30can be increased by obtaining the VO positional information 127 from thecommunication terminal 30 more frequently. In addition, in step S22, thesecond communication unit 105 may request the current position of thecommunication terminal 30 from the communication terminal 30 and receivethe current position of the communication terminal 30 from thecommunication terminal 30.

Next, in step S23, the notification section 114 calculates a distancebetween the controller 20 and the communication terminal 30 on the basisof the distance between the controller 20 and the communication terminal30.

Next, in step S24, the notification section 114 reads the flightpossible distance from the flight possible area table 122 stored in thestorage unit 108. The notification section 114 reads a flight possibledistance in a top row in a first operation, and then sequentially readsflight possible distances in lower rows in second and later operations.

Next, in step S25, the notification section 114 calculates the sum of afirst flight possible distance, which is a radius of the first flightpossible area 2 around the controller 20, and a second flight possibledistance, which is a radius of the second flight possible area 4 aroundthe communication terminal 30. In the second embodiment, the first andsecond flight possible distances are the same, and the flight possibledistance read from the flight possible area table 122 is used as thefirst and second flight possible distances.

Next, in step S26, the notification section 114 determines whether thedistance between the controller 20 and the communication terminal 30 islarger than the sum of the first and second flight possible distances.If determining that the distance between the controller 20 and thecommunication terminal 30 is equal to or smaller than the sum of thefirst and second flight possible distances (NO in step S26), thenotification section 114, in step S27, determines whether all the flightpossible distances in the flight possible area table 122 have been read.If the notification section 114 determines that all the flight possibledistances in the flight possible area table 122 have been read (YES instep S27), the process returns to step S21. If the notification section114 determines that not all the flight possible distances in the flightpossible area table 122 have been read (NO in step S27), on the otherhand, the process returns to step S24, and the notification section 114reads a flight possible distance in a next row of the flight possiblearea table 122 stored in the storage unit 108.

If determining that the distance between the controller 20 and thecommunication terminal 30 is larger than the sum of the first and secondflight possible distances (YES in step S26), on the other hand, thenotification section 114, in step S28, notifies the controller 20 thatthe first and second flight possible areas 2 and 4 will be separatedfrom each other. At this time, the notification section 114 may notifythe controller 20 of a time at which the first and second flightpossible areas 2 and 4 will be separated from each other, as well asthat the first and second flight possible areas 2 and 4 will beseparated from each other. The notification section 114 may also notifythe controller 20 that the drone 10 will be caused to move into thefirst flight possible area 2 around the controller 20 after the firstand second flight possible areas 2 and 4 are separated from each other.

A timing at which the notification section 114 notifies the controller20 that the first and second flight possible areas 2 and 4 will beseparated from each other may be determined in accordance with thedistance between the controller 20 and the drone 10. That is, the drone10 needs to return to the controller 20 or the communication terminal30. If the distance between the controller 20 and the drone 10 is large,time taken to return to the controller 20 is long. The notificationsection 114, therefore, issues a notification earlier as the distancebetween the controller 20 and the drone 10 becomes larger. For example,the notification section 114 calculates time taken for the drone 10 toreturn to the controller 20 on the basis of the distance between thecontroller 20 and the drone 10 and a maximum speed of the drone 10. Thenotification section 114 may then notify, at a timing obtained bysubtracting the return time from the time at which the first and secondflight possible areas 2 and 4 will be separated from each other, thecontroller 20 that the first and second flight possible areas 2 and 4will be separated from each other.

Alternatively, the notification section 114 may notify the controller 20that the first and second flight possible areas 2 and 4 are separatedfrom each other when the first and second flight possible areas 2 and 4are separated from each other.

Next, a process for controlling the flight of the drone 10 according tothe second embodiment will be described.

FIG. 12 is a first flowchart illustrating the process for controllingthe flight of the drone 10 according to the second embodiment of thepresent disclosure. FIG. 13 is a second flowchart illustrating theprocess for controlling the flight of the drone 10 according to thesecond embodiment of the present disclosure. FIG. 14 is a thirdflowchart illustrating the process for controlling the flight of thedrone 10 according to the second embodiment of the present disclosure.

First, in step S31, the time measuring unit 101 obtains the presenttime.

Next, in step S32, the flight possible area changing section 112 refersto the flight possible area table 122 and determines whether the firstand second flight possible areas 2 and 4 are to be changed now. A timeto change the first flight possible area 2 and a time to change thesecond flight possible area 4 are the same. If the flight possible areachanging section 112 determines that the first and second flightpossible areas 2 and 4 are not to be changed now (NO in step S32), theprocess returns to step S31.

If determining that the first and second flight possible areas 2 and 4are to be changed now (YES in step S32), the flight possible areachanging section 112, in step S33, determines the first and secondflight possible areas 2 and 4 of the drone 10 in accordance with thedifference between the time of sunset and the present time. If thedifference between the time of sunset and the present time is 30minutes, for example, the flight possible area changing section 112refers to the flight possible area table 122 and determines a hemispherewhose center is the controller 20 and whose radius is 50 m as the firstand second flight possible areas 2 and 4. The flight possible areachanging section 112 stores the determined first and second flightpossible areas 2 and 4 in the storage unit 108 as the flight possiblearea information 125.

In the second embodiment, the first and second flight possible areas 2and 4 have the same flight possible distance, and the flight possiblearea read from the flight possible area table 122 is used as the firstand second flight possible areas 2 and 4.

The first flight possible distance of the first flight possible area 2and the second flight possible distance of the second flight possiblearea 4 may be different from each other. In this case, the storage unit108 stores the flight possible area table 122 in which certain timeperiods before sunset, first flight possible areas 2, and second flightpossible areas 4 are associated with one another.

In addition, if the current positions of the drone 10 and the controller20 include latitude information, longitude information, and altitudeinformation, the first and second flight possible areas 2 and 4 haveshapes of hemispheres whose centers are the current position of thecontroller 20 and whose radii are the first and second flight possibledistances, respectively. If the current positions of the drone 10 andthe controller 20 include latitude information and longitude informationbut do not include altitude information, the first and second flightpossible areas 2 and 4 have shapes of circles whose centers are thecurrent position of the controller 20 and whose radii are the first andsecond flight possible distances, respectively.

Next, in step S34, the flight possible area changing section 112 readsthe controller positional information 123 from the storage unit 108 toobtain the current position of the controller 20. Although thecontroller positional information 123 stored in the storage unit 108does not necessarily indicate the current position of the controller 20,the accuracy of identification of the current position of the controller20 can be increased by obtaining the controller positional information123 from the controller 20 more frequently. In addition, in step S34,the second communication unit 105 may request the current position ofthe controller 20 from the controller 20 and receive the currentposition of the controller 20 from the controller 20.

Next, in step S35, the flight possible area changing section 112 readsthe VO positional information 127 from the storage unit 108 to obtainthe current position of the communication terminal 30. Although the VOpositional information 127 stored in the storage unit 108 does notnecessarily indicate the current position of the communication terminal30, the accuracy of identification of the current position of thecommunication terminal 30 can be increased by obtaining the VOpositional information 127 from the communication terminal 30 morefrequently. In addition, in step S35, the second communication unit 105may request the current position of the communication terminal 30 fromthe communication terminal 30 and receive the current position of thecommunication terminal 30 from the communication terminal 30.

Next, in step S36, the flight possible area changing section 112calculates the distance between the controller 20 and the communicationterminal 30 on the basis of the current positions of the controller 20and the communication terminal 30.

Next, in step S37, the flight possible area changing section 112calculates the sum of the first flight possible distance, which is theradius of the first flight possible area 2 around the controller 20, andthe second flight possible distance, which is the radius of the secondflight possible area 4 around the communication terminal 30.

Next, in step S38, the flight possible area changing section 112determines whether the distance between the controller 20 and thecommunication terminal 30 is larger than the sum of the first and flightpossible distances. That is, if the distance between the controller 20and the communication terminal 30 is larger than the sum of the firstand flight possible distances, the first and second flight possibleareas 2 and 4 do not overlap, that is, are separated from each other.

If the flight possible area changing section 112 determines that thedistance between the controller 20 and the communication terminal 30 islarger than the sum of the first and second flight possible distances(YES in step S38), the position measuring unit 102, in step S39, obtainsthe current position of the drone 10.

Next, in step S40, the flight possible area changing section 112calculates the distance between the drone 10 and the controller 20 onthe basis of the current positions of the drone 10 and the controller20.

Next, in step S41, the flight possible area changing section 112determines whether the drone 10 is located within the first flightpossible area 2 on the basis of the distance between the drone 10 andthe controller 20 and the first flight possible area 2. That is, theflight possible area changing section 112 compares the distance betweenthe drone 10 and the controller 20 with the first flight possibledistance and, if the distance between the drone 10 and the controller 20is equal to or smaller than the first flight possible distance,determines that the drone 10 is located within the first flight possiblearea 2 or, if the distance between the drone 10 and the controller 20 islarger than the first flight possible distance, determines that thedrone 10 is not located within the first flight possible area 2.

If the flight possible area changing section 112 determines that thedrone 10 is located within the first flight possible area 2 (YES in stepS41), the flight control section 111, in step S42, accepts an operationcommand from the controller 20 and flies the drone 10 in accordance withthe operation command. Step S42 is the same as step S8 illustrated inFIG. 6 .

If the flight possible area changing section 112 determines that thedrone 10 is not located within the first flight possible area 2 (NO instep S41), on the other hand, the forcible movement control section 113,in step S43, forcibly moves the drone 10 toward the controller 20 sothat the drone 10 enters the first flight possible area 2. At this time,the forcible movement control section 113 does not accept an operationcommand from the controller 20 until the drone 10 enters the firstflight possible area 2.

Next, in step S44, the notification section 114 notifies the controller20 that the drone 10 is to be forcibly moved toward the controller 20.The process returns to step S41, and the forcible movement controlsection 113 automatically flies the drone 10 toward the controller 20until the drone 10 enters the first flight possible area 2.

If the flight possible area changing section 112 determines in step S38that the distance between the controller 20 and the communicationterminal 30 is equal to or smaller than the sum of the first and secondflight possible distances (NO in step S38), on the other hand, theposition measuring unit 102, in step S45, obtains the current positionof the drone 10.

Next, in step S46, the flight possible area changing section 112calculates the distance between the drone 10 and the controller 20 onthe basis of the current positions of the drone 10 and the controller20.

Next, in step S47, the flight possible area changing section 112calculates the distance between the drone 10 and the communicationterminal 30 on the basis of the current positions of the drone 10 andthe communication terminal 30.

Next, in step S48, the flight possible area changing section 112determines whether or not the drone 10 is located within the firstflight possible area 2 or the second flight possible area 4 on the basisof the distance between the drone 10 and the controller 20, the distancebetween the drone 10 and the communication terminal 30, the first flightpossible area 2, and the second flight possible area 4. That is, theflight possible area changing section 112 compares the distance betweenthe drone 10 and the controller 20 with the first flight possibledistance and, if the distance between the drone 10 and the controller 20is equal to or smaller than the first flight possible distance,determines that the drone 10 is located within the first flight possiblearea 2. The flight possible area changing section 112 compares thedistance between the drone 10 and the communication terminal 30 with thesecond flight possible distance and, if the distance between the drone10 and the communication terminal 30 is equal to or smaller than thesecond flight possible distance, determines that the drone 10 is locatedwithin the second flight possible area 4. If the distance between thedrone 10 and the controller 20 is larger than the first flight possibledistance and if the distance between the drone 10 and the communicationterminal 30 is larger than the second flight possible distance, theflight possible area changing section 112 determines that the drone 10is not located within the first flight possible area 2 or the secondflight possible area 4.

If the flight possible area changing section 112 determines that thedrone 10 is located within the first flight possible area 2 or thesecond flight possible area 4 (YES in step S48), the flight controlsection 111, in step S49, accepts an operation command from thecontroller 20 and flies the drone 10 in accordance with the operationcommand. Step S49 is the same as step S8 illustrated in FIG. 6 .

If the flight possible area changing section 112 determines that thedrone 10 is not located within the first flight possible area 2 or thesecond flight possible area 4 (NO in step S48), on the other hand, theforcible movement control section 113, in step S50, forcibly moves thedrone 10 toward the controller 20 so that the drone 10 enters the firstflight possible area 2. At this time, the forcible movement controlsection 113 does not accept an operation command from the controller 20until the drone 10 enters the first flight possible area 2.

Next, in step S51, the notification section 114 notifies the controller20 that the drone 10 is to be forcibly moved toward the controller 20.The process returns to step S48, and the forcible movement controlsection 113 automatically flies the drone 10 toward the controller 20until the drone 10 enters the first flight possible area 2.

FIG. 15 is a schematic diagram illustrating separation between the firstand second flight possible areas 2 and 4 according to the secondembodiment. In FIG. 15 , the drone 10, the controller 20, and thecommunication terminal 30 are viewed from above. In FIG. 15 , the flightpossible area changing section 112 determines, at the first time, whichis the certain period of time before sunset, the first flight possiblearea 2 whose center is the controller 20 and whose radius is a firstflight possible distance FFD1 and the second flight possible area 4whose center is the communication terminal 30 and whose radius is asecond flight possible distance SFD1. The flight possible area changingsection 112 then determines, at the second time, which is closer to thetime of sunset than the first time is, a first flight possible area 21whose center is the controller 20 and whose radius is a first flightpossible distance FFD2, which is smaller than the first flight possibledistance FFD1, and a second flight possible area 41 whose center is thecommunication terminal 30 and whose radius is a second flight possibledistance SFD2, which is smaller than the second flight possible distanceSFD1.

As described above, when the first and second flight possible areas 2and 4 are reduced, the first and second flight possible areas 21 and 41might be separated from each other. If the drone 10 is located halfwaybetween the controller 20 and the communication terminal 30 at thistime, the drone 10 might not be located within the first flight possiblearea 21 or the second flight possible area 41. If the first and secondflight possible areas 2 and 4 will be reduced and the first and secondflight possible areas 21 and 41 will be separated from each other,therefore, the controller 20 is notified that the first and secondflight possible areas 21 and 41 will be separated from each other, inorder to avoid a situation in which the drone 10 is not located withinthe first flight possible area 21 or the second flight possible area 41.

In addition, in the second embodiment, if the first and second flightpossible areas 2 and 4 are separated from each other, the drone 10 needsto move into the first flight possible area 2 around the controller 20.If the first and second flight possible areas 2 and 4 will be separatedfrom each other, therefore, the controller 20 is notified that the drone10 needs to move into the first flight possible area 2, but the presentdisclosure is not particularly limited to this. If the first and secondflight possible areas 2 and 4 are separated from each other, the drone10 may enter either the first flight possible area 2 around thecontroller 20 or the second flight possible area 4 around thecommunication terminal 30. In this case, when the first and secondflight possible areas 2 and 4 are separated from each other, thecontroller 20 may be notified that the drone 10 needs to move into thefirst flight possible area 2 around the controller 20 or the secondflight possible area 4 around the communication terminal 30.

At this time, the notification section 114 may estimate, before theflight possible area changing section 112 determines the first andsecond flight possible areas 2 and 4, whether the drone 10 will belocated outside the first and second flight possible areas 2 and 4 whenthe first and second flight possible areas 2 and 4 are determined. Ifestimating that the drone 10 will be located outside the first andsecond flight possible areas 2 and 4, the notification section 114 maytransmit, to the controller 20, guidance information for guiding thedrone 10 into the first flight possible area 2 or the second flightpossible area 4.

If the first and second flight possible areas 2 and 4 will be separatedfrom each other at 5 p.m., for example, the drone 10 may transmitguidance information to the controller 20 at 4 p.m., which says “Flightpossible areas will be separated from each other. Move drone into flightpossible area around operator or VO”.

In addition, although the controller 20 is notified that the first andsecond flight possible areas 2 and 4 will be separated from each otherin the second embodiment, the present disclosure is not particularlylimited to this. A terminal (e.g., a smartphone, etc.) carried by theoperator 1 may be notified instead of the controller 20.

In addition, if the drone 10 will be located outside the first andsecond flight possible areas 2 and 4 when the first and second flightpossible areas 2 and 4 are determined, the forcible movement controlsection 113 may automatically move the drone 10 toward the controller 20or the communication terminal 30, whichever is closer to the drone 10.

In addition, the operator 1 or the VO 3 might move in the secondembodiment. The separation notification process illustrated in FIG. 11may be regularly performed, and the controller 20 may be notified ofseparation between the first and second flight possible areas 2 and 4 inreal-time.

In addition, in the second embodiment, the controller 20 may include thetime measuring unit 101, the flight possible area changing section 112,the forcible movement control section 113, the flight possible areatable 122, the forcible movement program 124, the flight possible areainformation 125, the sunset information 126, and the VO positionalinformation 127. In this case, the forcible movement control section 113has a function of generating and transmitting a command for forciblymoving the drone 10. The forcible movement program 124 is used togenerate and transmit a command for forcibly moving the drone 10. Theflight possible area table 122, the forcible movement program 124, theflight possible area information 125, the sunset information 126, andthe VO positional information 127 are stored in the storage unit of thecontroller 20. The storage unit also stores positional informationregarding the drone 10. As a result, the controller 20 can perform theprocesses performed by the drone 10 in the above description. Inaddition, the VO positional information 127 transmitted from thecommunication terminal 30 may be received by the controller 20 through aserver.

In addition, in the second embodiment, the flight control system mayinclude the drone 10, the controller 20 and a server. The server isconnected to the controller 20 through a network. The server may includethe time measuring unit 101, the flight possible area changing section112, the forcible movement control section 113, the flight possible areatable 122, the forcible movement program 124, the flight possible areainformation 125, the sunset information 126, and the VO positionalinformation 127. In this case, the forcible movement control section 113has a function of generating and transmitting a command for forciblymoving the drone 10. The forcible movement program 124 is used togenerate and transmit a command for forcibly moving the drone 10. Theflight possible area table 122, the forcible movement program 124, theflight possible area information 125, the sunset information 126, andthe VO positional information 127 are stored in a storage unit of theserver. The storage unit also stores positional information regardingthe drone 10. As a result, the server can perform the processesperformed by the drone 10 in the above description. Informationtransmitted from the server may be received by the drone 10 through thecontroller 20, and information transmitted from the drone 10 may bereceived by the server through the controller 20. Alternatively,information transmitted from the server may be directly received by thedrone 10, and information transmitted from the drone 10 may be directlyreceived by the server. Information transmitted from the communicationterminal 30 may be received by the server through the controller 20 ordirectly received by the server.

Now, a case in which there are a plurality of VOs in the secondembodiment will be described.

FIG. 16 is a schematic diagram illustrating separation between the firstflight possible area 2, the second flight possible area 4, and a thirdflight possible area 5. In the example illustrated in FIG. 16 , theflight control system includes the drone 10, the controller 20, a firstcommunication terminal 31, and a second communication terminal 32. Thefirst communication terminal 31 is operated by a first VO who monitorsthe drone 10. The second communication terminal 32 is operated by asecond VO who monitors the drone 10 at a position different from aposition of the first VO. The configuration of the first communicationterminal 31 and the second communication terminal 32 is the same as thatof the communication terminal 30.

In FIG. 16 , the drone 10, the controller 20, the first communicationterminal 31, and the second communication terminal 32 are viewed fromabove. In FIG. 16 , the flight possible area changing section 112determines, at the first time, which is the certain period of timebefore sunset, the first flight possible area 2 whose center is thecontroller 20 and whose radius is the first flight possible distance,the second flight possible area 4 whose center is the firstcommunication terminal 31 and whose radius is the second flight possibledistance, and the third flight possible area 5 whose center is thesecond communication terminal 32 and whose radius is a third flightpossible distance. The flight possible area changing section 112 thendetermines, at the second time, which is closer to the time of sunsetthan the first time is, the first flight possible area 21 whose centeris the controller 20 and whose radius is the reduced first flightpossible distance, the second flight possible area 41 whose center isthe first communication terminal 31 and whose radius is the reducedsecond flight possible distance, and a third flight possible area 51whose center is the second communication terminal 32 and whose radius isthe reduced third flight possible distance.

In FIG. 16 , as a result of the reduction of the first to third flightpossible areas 2, 4, and 5, the first and third flight possible areas 21and 51 are separated from the second flight possible area 41. The firstflight possible area 21 overlaps the third flight possible area 51.

When the first and third flight possible areas 21 and 51 are separatedfrom the second flight possible area 41, the drone 10 might need to belocated within the first flight possible area 21 around the controller20. At this time, the third flight possible area 51, which is notseparated from the first flight possible area 21, may be regarded as apart of the first flight possible area 21.

If the first flight possible area 21 based on the position of thecontroller 20 and the third flight possible area 51 based on a positionof the second communication terminal 32 operated by the second VO whomonitors the drone 10 are separated from the second flight possible area41 based on a position of the first communication terminal 31 operatedby the first VO who monitors the drone 10 and the first flight possiblearea 21 overlaps the third flight possible area 5 after the flightpossible area changing section 112 determines the first to third flightpossible areas 21, 41, and 51, the notification section 114 may transmitinformation regarding the third flight possible area 51, which is notseparated from the first flight possible area 21, to the controller 20.At this time, the flight control section 111 may control the drone 10such that the drone 10 flies within the first flight possible area 21 orthe third flight possible area 51.

Alternatively, if the first and third flight possible areas 21 and 51are separated from the second flight possible area 41 and the firstflight possible area 2 overlaps the third flight possible area 51 afterthe flight possible area changing section 112 determines the first tothird flight possible areas 21, 41, and 51, the forcible movementcontrol section 113 may automatically move the drone 10 toward thecontroller 20 or the second communication terminal 32, whichever iscloser to the drone 10.

When the first to third flight possible areas 2, 4, and 5 are reduced,the first to third flight possible areas 21, 41, and 51 might not beseparated from one another.

FIG. 17 is a schematic diagram illustrating overlap between the first tothird flight possible areas 2, 4, and 5 according to the secondembodiment. In the example illustrated in FIG. 17 , the flight controlsystem includes the drone 10, the controller 20, the first communicationterminal 31, and the second communication terminal 32. The firstcommunication terminal 31 is operated by the first VO who monitors thedrone 10 and the second communication terminal 32 is operated by thesecond VO who monitors the drone 10 at the position different from thatof the first VO.

In FIG. 17 , the drone 10, the controller 20, the first communicationterminal 31, and the second communication terminal 32 are viewed fromabove. In FIG. 17 , the flight possible area changing section 112determines, at the first time, which is the certain period of timebefore sunset, the first flight possible area 2 whose center is thecontroller 20 and whose radius is the first flight possible distance,the second flight possible area 4 whose center is the firstcommunication terminal 31 whose radius is the second flight possibledistance, and the third flight possible area 5 whose center is thesecond communication terminal 32 and whose radius is the third flightpossible distance. The flight possible area changing section 112 thendetermines, at the second time, which is closer to the time of sunsetthan the first time is, the first flight possible area 21 whose centeris the controller 20 and whose radius is the reduced first flightpossible distance, the second flight possible area 41 whose center isthe first communication terminal 31 and whose radius is the reducedsecond flight possible distance, and the third flight possible area 51whose center is the second communication terminal 32 and whose radius isthe reduced third flight possible distance.

In FIG. 17 , as a result of the reduction of the first to third flightpossible areas 2, 4, and 5, the first flight possible area 21 overlapsthe third flight possible area 51, and the second flight possible area41 overlaps the third flight possible area 51. Although the first flightpossible area 21 is separated from the second flight possible area 41but connected to the second flight possible area 41 through the thirdflight possible area 51. When the first to third flight possible areas21, 41, and 51 are connected to one another, the drone 10 may fly withinthe first flight possible area 21, the second flight possible area 41,or the third flight possible area 51.

If the first to third flight possible areas 21, 41, and 51 are furtherreduced as time elapses, the first flight possible area 21 might beseparated from the second flight possible area 41, or the second flightpossible area 41 might be separated from the third flight possible area51. In this case, it is difficult for the drone 10 located within thesecond flight possible area 41 or the third flight possible area 51 toreturn to the first flight possible area 21.

If the first flight possible area 21 based on the position of thecontroller 20 is separated from the second flight possible area 41 basedon the position of the first communication terminal 31 operated by thefirst VO who monitors the drone 10 and the third flight possible area 51based on the position of the second communication terminal 32 operatedby the second VO who monitors the drone 10 overlap the first and secondflight possible areas 21 and 41 after the flight possible area changingsection 112 determines the first to third flight possible areas 21, 41,and 51, the notification section 114 may transmit, to the controller 20,guidance information for guiding the drone 10 into the first flightpossible area 21 or the third flight possible area 51 adjacent to thefirst flight possible area 21.

In addition, if the first flight possible area 21 is separated from thesecond flight possible area 41, the third flight possible area 51overlaps the first and second flight possible areas 21 and 41, and thedrone 10 is located outside the first flight possible area 21 and thethird flight possible area 51 after the flight possible area changingsection 112 determines the first to third flight possible areas 21, 41,and 51, the forcible movement control section 113 may forcibly move thedrone 10 toward the controller 20 or the second communication terminal32 so that the drone 10 enters the first flight possible area 21 or thethird flight possible area 51.

If the first flight possible area 21 is separated from the second flightpossible area 41, the third flight possible area 51 overlaps the firstand second flight possible areas 21 and 41, and the drone 10 is locatedoutside the first to third flight possible areas 21, 41, and 51 afterthe flight possible area changing section 112 determines the first tothird flight possible areas 21, 41, and 51, the forcible movementcontrol section 113 may forcibly move toward the controller 20 in thefirst flight possible area 21 or the second communication terminal 32 inthe third flight possible area 51, whichever is closer to the drone 10.

If the first to third flight possible areas 21, 41, and 51 are furtherreduced and the first to third flight possible areas 21, 41, and 51 areseparated from one another, the drone 10 may be moved into a largestflight possible area.

FIG. 18 is a schematic diagram illustrating a process for moving thedrone 10 into a largest one of the plurality of flight possible areas21, 41, and 51 separated from one another. In the example illustrated inFIG. 18 , the flight control system includes the drone 10, thecontroller 20, the first communication terminal 31, and the secondcommunication terminal 32. The first communication terminal 31 isoperated by the first VO who monitors the drone 10, and the secondcommunication terminal 32 is operated by the second VO who monitors thedrone 10 at the position different from that of the first VO.

In FIG. 18 , the drone 10, the controller 20, the first communicationterminal 31, and the second communication terminal 32 are viewed fromabove. In FIG. 18 , the flight possible area changing section 112determines, at the first time, which is the certain period of timebefore sunset, the first flight possible area 2 whose center is thecontroller 20 and whose radius is the first flight possible distance,the second flight possible area 4 whose center is the firstcommunication terminal 31 and whose radius is the second flight possibledistance, and the third flight possible area 5 whose center is thesecond communication terminal 32 and whose radius is the third flightpossible distance. The flight possible area changing section 112 thendetermines, at the second time, which is closer to the time of sunsetthan the first time is, the first flight possible area 21 whose centeris the controller 20 and whose radius is the reduced first flightpossible distance, the second flight possible area 41 whose center isthe first communication terminal 31 and whose radius is the reducedsecond flight possible distance, and the third flight possible area 51whose center is the second communication terminal 32 and whose radius isthe reduced third flight possible distance.

In FIG. 18 , as a result of the reduction of the first to third flightpossible areas 2, 4, and 5, the first flight possible area 21 isseparated from the second and third flight possible areas 41 and 51, andthe second flight possible area 41 overlaps the third flight possiblearea 51.

Here, the forcible movement control section 113 calculates the area ofthe plurality of flight possible areas 21, 41, and 51 and identifies alargest one of the plurality of flight possible areas 21, 41, and 51. Ifa plurality of flight possible areas overlap at this time, the forciblemovement control section 113 counts the plurality of overlapping flightpossible areas as one flight possible area and calculates the area ofthe plurality of overlapping flight possible areas. In the exampleillustrated in FIG. 18 , the second and third flight possible areas 41and 51 overlap, and the forcible movement control section 113 counts thesecond and third flight possible areas 41 and 51 as one flight possiblearea and calculates the area of a flight possible area including thesecond and third flight possible areas 41 and 51.

The forcible movement control section 113 then forcibly moves the drone10 toward the largest one of the plurality of flight possible areas 21,41, and 51. In the example illustrated in FIG. 18 , the flight possiblearea including the second and third flight possible areas 41 and 51 islarger than the first flight possible area 21. The forcible movementcontrol section 113, therefore, forcibly moves the drone 10 towardeither the second flight possible area 41 or the third flight possiblearea 51. At this time the forcible movement control section 113 forciblymoves the drone 10 toward the second flight possible area 41 or thethird flight possible area 51, whichever is closer to the drone 10.

Furthermore, in the second embodiment, the drone 10 may receive, beforethe first and second flight possible areas 2 and 4 are determined, aninput from the operator 1 indicating whether the drone 10 is to be movedinto the first flight possible area 2 or the second flight possible area4. The input indicating whether the drone 10 is to be moved into thefirst flight possible area 2 or the second flight possible area 4 may bestored in the storage unit before the first and second flight possibleareas 2 and 4 are determined.

FIG. 19 is a block diagram illustrating the configuration of a drone 10according to a modification of the second embodiment of the presentdisclosure.

The drone 10 illustrated in FIG. 19 includes the time measuring unit101, the position measuring unit 102, the driving unit 103, the firstcommunication unit 104, the second communication unit 105, the battery106, the control unit 107, and the storage unit 108. In the modificationof the second embodiment, description of the same components as in thefirst or second embodiment is omitted.

The control unit 107 includes the flight control section 111, the flightpossible area changing section 112, the forcible movement controlsection 113, and the notification section 114.

The storage unit 108 stores the flight basic program 121, the flightpossible area table 122, the controller positional information 123, theforcible movement program 124, the flight possible area information 125,the sunset information 126, the VO positional information 127, andmovement area information 128.

The movement area information 128 indicates whether the drone 10 is tobe moved into the first flight possible area 2 or the second flightpossible area 4 when the first and second flight possible areas 2 and 4are determined. The storage unit 108 stores the movement areainformation 128 in advance. For example, the controller 20 receives themovement area information 128 input from the operator 1 and transmitsthe received movement area information 128 to the drone 10. The secondcommunication unit 105 receives the movement area information 128transmitted from the controller 20 and stores the received movement areainformation 128 in the storage unit 108.

If the drone 10 is not located within the first flight possible area 2or the second flight possible area 4 indicated by the movement areainformation 128 when the first and second flight possible areas 2 and 4are actually determined, the forcible movement control section 113automatically moves the drone 10 toward the first flight possible area 2or the second flight possible area 4 stored in the storage unit 108.

The flight possible area changing section 112 reduces either the firstflight possible area 2 or the second flight possible area 4 indicated bythe movement area information 128 as time elapses.

If the storage unit 108 does not store the movement area information 128in advance and the drone 10 is not located within the first flightpossible area 2 or the second flight possible area 4 indicated by themovement area information 128 when the first and second flight possibleareas 2 and 4 are actually determined, the forcible movement controlsection 113 automatically moves the drone 10 toward the controller 20 orthe communication terminal 30, whichever is closer to the drone 10.

If the storage unit 108 does not store the movement area information 128in advance and the drone 10 is not located within the first flightpossible area 2 or the second flight possible area 4 indicated by themovement area information 128 when the first and second flight possibleareas 2 and 4 are actually determined, the forcible movement controlsection 113 may automatically move the drone 10 toward the controller20.

Furthermore, if the drone 10 is located within an area different fromone indicated by the movement area information 128 when the first andsecond flight possible areas 2 and 4 are actually determined, the flightcontrol section 111 may control the drone 10 such that the drone 10flies within the area within which the drone 10 is currently located.

In addition, in the modification of the second embodiment, too, theflight control system may include the drone 10, the controller 20, thefirst communication terminal 31, and the second communication terminal32. If, in FIG. 16 , the storage unit 108 does not store the movementarea information 128 in advance, and if the first and third flightpossible areas 21 and 51 are separated from the second flight possiblearea 41 and the first flight possible area 21 overlaps the third flightpossible area 51 when the flight possible area changing section 112determines the first to third flight possible areas 21, 41, and 51, forexample, the forcible movement control section 113 may automaticallymove the drone 10 toward the controller 20 or the second communicationterminal 32, whichever is closer to the drone 10.

In addition, if, in FIG. 18 , the storage unit 108 does not store themovement area information 128 in advance and the first flight possiblearea 21 is separated from the second and third flight possible areas 41and 51 and the second flight possible area 41 overlaps the third flightpossible area 51 when the flight possible area changing section 112determines the first to third flight possible areas 21, 41, and 51, theforcible movement control section 113 may automatically move the drone10 toward the first communication terminal 31 or the secondcommunication terminal 32 in the largest flight possible area includingthe second and third flight possible areas 41 and 51, whichever iscloser to the drone 10.

In addition, in the modification of the second embodiment, thecontroller 20 may include the time measuring unit 101, the flightpossible area changing section 112, the forcible movement controlsection 113, the flight possible area table 122, the forcible movementprogram 124, the flight possible area information 125, the sunsetinformation 126, the VO positional information 127, and the movementarea information 128. In this case, the forcible movement controlsection 113 has a function of generating and transmitting a command forforcibly moving the drone 10. The forcible movement program 124 is usedto generate and transmit a command for forcibly moving the drone 10. Theflight possible area table 122, the forcible movement program 124, theflight possible area information 125, the sunset information 126, the VOpositional information 127, and the movement area information 128 arestored in the storage unit of the controller 20. The storage unit alsostore positional information regarding the drone 10. As a result, thecontroller 20 can perform the processes performed by the drone 10 in theabove description.

In addition, in the modification of the second embodiment, the flightcontrol system may include the drone 10, the controller 20 and a server.The server is connected to the controller 20 through a network. Theserver may include the time measuring unit 101, the flight possible areachanging section 112, the forcible movement control section 113, theflight possible area table 122, the forcible movement program 124, theflight possible area information 125, the sunset information 126, the VOpositional information 127, and the movement area information 128. Inthis case, the forcible movement control section 113 has a function ofgenerating and transmitting a command for forcibly moving the drone 10.The forcible movement program 124 is used to generate and transmit acommand for forcibly moving the drone 10. The flight possible area table122, the forcible movement program 124, the flight possible areainformation 125, the sunset information 126, the VO positionalinformation 127, and the movement area information 128 are stored in astorage unit of the server. The storage unit also stores positionalinformation regarding the drone 10. As a result, the server can performthe processes performed by the drone 10 in the above description.Information transmitted from the server may be received by the drone 10through the controller 20, and information transmitted from the drone 10may be received by the server through the controller 20. Alternatively,information transmitted from the server may be directly received by thedrone 10, and information transmitted from the drone 10 may be directlyreceived by the server. Information transmitted from the communicationterminal 30 may be received by the server through the controller 20 ordirectly received by the server.

In the present disclosure, some or all of the units, the apparatuses,the members, and the sections or some of all of the functional blocksillustrated in the block diagrams of FIGS. 3, 4, 5, 12, 18, 19, and 22may be implemented by one or a plurality of electronic circuitsincluding a semiconductor device, a semiconductor integrated circuit(IC), or a large-scale integration (LSI) circuit. The LSI circuit or theIC may be mounted on a single chip, or may be constructed by combining aplurality of chips. For example, functional blocks other than a storagedevice may be integrated on a single chip. Although the terms “LSIcircuit” and “IC” are used here, a term used changes depending on adegree of integration, and a circuit called a “system LSI circuit”, a“very-large-scale integration (VLSI) circuit”, or a“ultra-large-scale-integration (ULSI) circuit” may be used, instead. Afield-programmable gate array (FPGA), which is programmed after an LSIcircuit is fabricated, or a reconfigurable logic device, which iscapable of reconfiguring connections inside an LSI circuit or settingcircuit sections inside an LSI circuit, can be used for the samepurpose.

Some or all the functions or the operations of the units, theapparatuses, the members, and the section may be implemented by asoftware process. In this case, software is stored in one or a pluralityof non-transitory recording media such as a read-only memory (ROM), anoptical disc, or a hard disk drive. When a processor executes thesoftware, a function specified by the software is achieved by theprocessor and peripheral devices. A system or an apparatus may includethe one or plurality of non-transitory recording media storing thesoftware, the processor, and a necessary hardware device, such as aninterface.

The drone, the method for controlling flight, the flight basic program,and the forcible movement program in the present disclosure are capableof returning the drone before an end of a time period for which theflight of the drone is permitted and effective as a drone flown byremote control, a method for controlling the flight of the drone flownby remote control, a flight basic program, and a forcible movementprogram, respectively.

What is claimed is:
 1. A drone, comprising: a motor; a plurality ofpropulsion propellers; a plurality of sensors; a controller; a timerthat measures a present time; a global positioning system that obtains acurrent position of the drone; and a storage that stores a time periodfor which flight of the drone is permitted, wherein the controllerperforms operations, including sequentially reducing a possible flightarea of the drone in accordance with a sequence of determineddifferences between an end of the time period for which flight of thedrone is permitted and the present time, wherein the end of the timeperiod for which flight of the drone is permitted is sunset, determiningwhether the drone is located within the possible flight area on thebasis of the current position of the drone, and controlling the drone tomove the drone within the possible flight area.
 2. The drone accordingto claim 1, wherein the operations further include moving, when it isdetermined that the drone is located outside the possible flight area,the drone toward a control device used to remotely control the drone. 3.The drone according to claim 1, wherein the operations further includechanging the possible flight area at a certain time.
 4. The droneaccording to claim 1, wherein the operations further include rejecting,when it is determined that the drone is located outside the possibleflight area, an operation command from a control device used to remotelycontrol the drone.
 5. The drone according to claim 1, wherein theoperations further include rejecting, when it is determined that thedrone is located outside the possible flight area, an operation otherthan the operation for moving the drone toward a control device used toremotely control the drone.
 6. A method for controlling flight of adrone, including a motor, propulsion propellers, sensors, a controller,a timer, a global positioning system, and a storage, the methodcomprising: obtaining a present time from the timer, obtaining a currentposition of the drone from the global positioning system, obtaining atime period, stored in the storage, for which the drone is permitted tofly, sequentially reducing, by the controller, a possible flight area ofthe drone in accordance with a sequence of determined differencesbetween an end of the time period for which flight of the drone ispermitted and the present time, wherein the end of the time period forwhich flight of the drone is permitted is sunset, determining, by thecontroller, whether the drone is located within the possible flight areaon the basis of the current position of the drone, and controlling, bythe controller, the drone to move the drone within the possible flightarea.
 7. A computer-readable non-transitory recording medium storing aprogram for controlling flight of a drone, including a motor, propulsionpropellers, sensors, a timer, a global positioning system, a computer,and a storage, the program causing, when executed by the computer, thecomputer to perform operations, comprising: obtaining a present time bythe timer, obtaining a current position of the drone by the globalpositional system, obtaining a time period, stored in the storage, forwhich flight of the drone is permitted, sequentially reducing, by thecomputer, a possible flight area of the drone in accordance with asequence of determined differences between an end of the time period forwhich flight of the drone is permitted and the present time, wherein theend of the time period for which flight of the drone is permitted issunset, determining, by the computer, whether the drone is locatedwithin the possible flight area on the basis of the current position ofthe drone, and controlling, by the computer, the drone to move the dronewithin the possible flight area.
 8. A method for notifying a controldevice used to remotely control a drone, including a motor, propulsionpropellers, sensors, a controller, a timer, a global positioning system,and a storage, the method comprising: obtaining a present time from thetimer, obtaining a current position of the drone by the globalpositioning system, obtaining a time period, from the storage, for whichflight of the drone is permitted, sequentially reducing, by thecontroller, a possible flight area of the drone in accordance with asequence of determined differences between an end of the time period forwhich flight of the drone is permitted and the present time, wherein theend of the time period for which flight of the drone is permitted issunset, notifying, by the controller, the control device that the flightpossible area has been determined, and controlling, by the controller,the drone to move the drone within the possible flight area.
 9. Themethod according to claim 8, wherein notifying includes notifying thecontrol device that the possible flight area is to be determined beforea determined possible flight area is set.
 10. The method according toclaim 8, wherein notifying includes notifying the control device thatthe drone is to be moved toward the control device when it is determinedthat the drone is located outside the possible flight area.
 11. Acomputer-readable, non-transitory recording medium storing a program fornotifying a control device used to remotely control a drone, including amotor, propulsion propellers, sensors, a computer, a timer, a globalpositioning system, and a storage, the program causing, when executed bythe computer, the computer to perform operations, comprising: obtaininga present time from the timer, obtaining a current position of the dronefrom the global positioning system, obtaining a time period, from thestorage, for which flight of the drone is permitted, sequentiallyreducing, by the computer, a possible flight area of the drone inaccordance with a sequence of determined differences between an end ofthe time period for which flight of the drone is permitted and thepresent time, wherein the end of the time period for which flight of thedrone is permitted is sunset, notifying, by the computer, the controldevice that the possible flight area has been determined, andcontrolling, by the computer, the drone to move the drone within thepossible flight area.
 12. The drone according to claim 1, wherein thestorage stores sunset information for which flight of the drone ispermitted.